Public Lab Research note

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Case Study: Using Aerial Imagery to Pressure Industrial Polluters into Stormwater Compliance

by gretchengehrke |

gretchengehrke was awarded the Basic Barnstar by warren for their work in this research note.

This is Part 1 of an ongoing series of case studies by Gretchen Gerhrke, Public Lab's Data Advocate, highlighting different stories of environmental data's use in the Public Lab community. You can find the entire series here.

Above, a false-color composite image incorporating near-infrared and visible-light photographs of a section of the Gowanus Canal, by the Gowanus Low-Altitude Mapping group.

Gowanus Canal in Brooklyn, New York has been an industrial hub since the nineteenth century. Historically, canal frontage has been used for coal yards, ship yards, dry docks, manufactured gas plants, and a variety of other industrial activities [1]. Due to historic and ongoing industrial contamination and sewage overflows, the U.S. Environmental Protection Agency declared the Gowanus Canal a Superfund site in March 2010 [2]. In addition to direct industrial discharges and raw sewage, stormwater runoff constitutes a significant ongoing source of contamination to Gowanus Canal, transporting metals, industrial chemicals, oils, and sediments from industrial surface yards into the Gowanus.

Riverkeeper is a member-supported watchdog organization dedicated to protecting the Hudson River, and is one of New York’s foremost clean water advocates. Riverkeeper’s boat captain John Lipscomb, and his assistant Neale Gulley, routinely patrol the Gowanus Canal to document environmental conditions and spot polluters, and Riverkeeper also maintains a hotline and website for R the public to report pollution [3]. When Riverkeeper identifies pollution problems in New York City waters, they often work with Super Law Group, LLC, an environmental law firm with deep expertise in the Clean Water Act that specializes in representing individual citizens and non-profit groups [4].

In 2012, following boat patrols and public complaints about stormwater pollution in the Gowanus Canal, a team of researchers and lawyers from Riverkeeper and Super Law Group launched a deeper investigation of local sources of stormwater pollution. The team used a combination of Google Maps and the New York City Digital Tax Map to obtain basic information about industrial companies along the canal, but they needed higher resolution images to provide information about actual operations.

A DIY near-infrared map of a section of the Gowanus Canal from July 31, 2011. View on MapKnitter

During an internet search, one member of the team, Edan Rotenberg of Super Law Group, was intrigued to discover infrared images of the Gowanus Canal, captured using a balloon-rigged infrared camera, posted on the Public Lab website [5]. Edan contacted Public Lab’s Director of Community Development, Liz Barry, who connected Edan with Eymund Diegel. Eymund is a lead community researcher on the Gowanus Canal, working with Proteus Gowanus and the Gowanus Canal Conservancy, and serves on the Board of Directors of Public Lab. The Gowanus Canal Conservancy and Public Lab collaborate on a project called Gowanus Low Altitude Mapping (GLAM) [6]. Through GLAM, Eymund and other community members have taken hundreds of high-resolution aerial photographs using balloon and kite cameras. Eymund shared these photographs with Edan.

Riverkeeper and Super Law Group sorted the GLAM aerial photographs, looking for clear photographs of industrial plots on the shoreline. In the low-altitude shoreline photographs, the team looked for evidence of faulty equipment or practices that broke permit regulations, such as broken fences that allowed debris to enter the canal, unauthorized open pits, and direct runoff from impermeable paved surfaces into the canal. In a few instances, Riverkeeper and Super Law Group approached companies that were implicated in the GLAM photographs and the companies responded by voluntarily cleaning up their operations without a lawsuit being filed. In another instance, Edan actually showed a company the images captured by GLAM, which pressured the company into compliance. In other cases, Riverkeeper and Super Law Group filed suit against the polluters, and used Public Lab community-collected aerial images to demonstrate that there was clear proof of pollution, which helped Riverkeeper reach settlements with those polluters that terminated the lawsuits quickly and brought those companies into prompt compliance with pollution laws.

While the Public Lab images were useful to this enforcement effort, there are additional features and collection strategies that would improve the utility of Public Lab aerial images for people interested in initiating similar efforts. A key feature to develop or include would be the automatic logging of date, time, location, and photographer in order to create an automatic start to the chain of custody for the image. The auto-logged location also would enable a person to utilize Public Lab images in other geospatial platforms, such as three-dimensional Geographic Information System (GIS) programs. Possibly the most noteworthy way to improve the utility of Public Lab images, based on Super Law Group’s experience, is to take more frequent images, creating a time series over the course of days, weeks, and months. Time series images are useful for legal proceedings to demonstrate consistent or repeated behaviors, or to demonstrate the progression of a problem. Thermal imagery is also extremely useful for detecting errant water inflows into a larger waterbody, including both stormwater runoff and groundwater discharges from seeps or pipes. These inflows can be difficult to discern with standard photography but often are a different temperature from the receiving water and therefore are distinguishable in thermal images. Near-infrared images can also be useful in identifying different source waters by imaging different algal communities. It was the GLAM infrared imagery that first attracted Edan to Public Lab resources, and he had hoped there would be a more extensive repository of infrared (and thermal) images. Edan postulates that environmental advocates and researchers nationwide would benefit tremendously from easier access to time-series visual and thermal aerial imagery.

Aerial photographs provide stakeholders and legislative decision-makers with compelling visual evidence. Aerial images can demonstrate the wide range of potential contamination pathways into a waterbody, and also remind people of the connectivity of the watershed. Thus, low-altitude high-resolution aerial images may be useful in promoting better environmental regulations and outcomes.

Works Cited:

  3. 1-800-21-RIVER ext 231;

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Hi Gretchen,
The Public Lab infrared images you refer to here are not thermal images. The near infrared photos don't have any information about temperature but are useful for studying plants because of the unique way chlorophyll reflects near infrared light. Also, the infrared map you link to at has spam in the description field, which sort of detracts from the message.

Hi Chris, Thanks for the note! Good point -- I did not link to a thermal image there, nor use one for the lead image. I will sort through MapKnitter to find the correct images!
Best, Gretchen

It's not just these particular photos, the Public Lab infrared cameras do not record thermal information. They are all near infrared cameras intended for vegetation analysis and don't tell us anything about temperature.

Hi Chris, Edan, whom I interviewed for this, was pretty adamant that the photos he saw and used were thermal images. I know specific kinds of cameras are necessary to record at those wavelengths (~10,000 nm, I believe), but I think the team was equipped with that sort of camera on their balloon rig. I will verify that with Edan and edit if necessary! Gretchen

Given the extreme cost of thermal imaging systems I don't know that anyone in PL has flown a FLIR on kite or balloon (or at least I can't find it in a search) though I think I ran across a article on someone using a thermal fishing BOB in that area (which is standard photographic imaging of a temperature indication device). I would be interested in seeing a thermal map of that area. I think you could gain insights on thermal or other pollution in NIR imagery by noting plant and algae status.

Ecta64, that's a good point. Liz confirmed that they never used thermal imaging system on the Gowanus, so it must have been a miscommunication about the type of IR imaging conducted. I'll edit and update immediately. Chris, thank you so much for catching this mistake!

There may have been confusion in part because some of the winter images GLAM took show trails where inflows melted ice, whether due to the flow of water or the different temperature of the inflow. So in a sense those images may have documented a thermal difference, even just with a regular photograph, as in this map:

The lead image is nice -- it's from this note:


true - images of melting ice was used by community members as "thermal clues" when searching for unknown/undocumented inflows into the canal.

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